The Teradek 11-0865 are designed special horizontally polarized antennas for use with the V antennas. Using a pair of H and a pair of V antennas on the TX improves the diversity characteristics of the system by combining the two perpendicular polarizations. For this H+V antenna configuration, two H antennas should be used at the TX and two at the RX as pictured. This configuration should allow for better reception and better video quality in medium-range situations and/or when the environment will create a lot of reflections for the wireless signal.
The combination of H and V antenna signals achieves better diversity than V antennas alone, especially while shooting outdoors. H antennas cause the RF signal from the transmitter to propagate in a perpendicular manner compared to the vertical signal from the V antenna.